A tragic new twist was added to the Middle East conflict when three 14-year-old Palestinian classmates were buried in Gaza yesterday after mounting a futile attack that ended with them being shot dead by Israeli soldiers.

They were victims of a disturbing trend among Palestinian children to copy their elders by participating in the 19-month-old uprising and are among the youngest Palestinian combatants to be killed yet. They reflect a desperate desire for revenge in Palestinian areas over the four-week-old Israeli offensive on the West Bank.

The three boys packed away their bags after school on Tuesday afternoon at the Sheikh Rudwan district in Gaza City, told their parents they were going to visit friends and set off to attack one of the isolated Jewish settlements dotted about Palestinian Gaza.

They launched their attack armed with four knives, an axe and crude, homemade explosives, but did not even get within striking range. Israeli soldiers shot them dead around midnight as the three crawled towards the settlement.

Thousands of Palestinians marched behind the coffins of the three schoolboys to a cemetery in Gaza City. The boys who were killed knew their mission was doomed as all three left suicide notes for their families saying that they were seeking "martyrdom" and asking forgiveness.

Many parents in Gaza, in spite of the long list of grisly incidents produced by the Israeli-Palestinian conflict, expressed horror that children as young as these had been drawn in and feared for their own children.

Even Hamas, the Islamic militant group responsible for sending most of the suicide bombers against Israel, expressed horror and described the schoolboys' actions as a "national catastrophe".

The boys were not attached to any military group but were acting on their own.

Palestinian children have suffered disproportionately in the uprising. Many of them have been shot by the Israeli army while throwing stones at tanks or at soldiers. But it has been rare for children to attempt to repeat the activities of Hamas and the other armed Palestinian groups, such as Islamic Jihad and the military wings of Fatah.

Tawfiq Salman, a psychiatrist in Bethlehem who works with children and carried out a survey, said: "Ninety per cent of Palestinian children suffer from post-traumatic stress syndrome as a result of the Israeli closures and the shootings."

Fadel Abu Heen, a psychologist, said many children were severely traumatised by seeing and hearing of Palestinians, especially children their own age, being killed by the Israelis. "It is despair, despair and more despair. Children are unable to cope with the sad reality," he said, adding that child suicide attackers were motivated more by an overwhelming sense of hopelessness than surging nationalism.

Mr Abu Heen blamed graphic televised scenes of burned and dismembered bodies shown repeatedly on Arab television. He urged militant leaders and religious leaders to wake up to the risks and work to restrain suicidal adolescent impulses.

"We should not militarise the whole society. A schoolchild must study and a grown-up fighter can fight," he said.

After leaving their homes, the three boys - Youssef Zaqout, Anwar Hamdouna and Ismail Abu Nadi - marched six kilometres to Netzarim settlement. About 6,000 Jewish settlers have opted to live among Gaza's 1.1 million Palestinians and are protected by about 10,000 Israeli soldiers.

Netzarim has become a symbol among the Palestinians of Gaza, the scene of many attacks and deaths, including Mohammed al-Durah, a child of 12 killed in the early days of the uprising while sheltering behind his father. Most Palestinians in Gaza have little contact with Israelis other than those in uniform.

The deaths of the children created little initial impact in Israel, just logged by the Israel army in the daily diary as one of a long list of violent incidents on the West Bank and Gaza. An Israeli army spokeswoman said last night: "The IDF identified three suspicious figures crawling a number of metres away from the fence that protects Netzarim. They opened fire and the three were killed."

Their bullet-riddled bodies were returned to their parents.

The IDF spokeswoman said they had been carrying "an explosive device - not a pipebomb - a hand grenade, an axe and four knives".

In his farewell note, Zaqout wrote: "Oh mother, please be happy with me. I ask you to pray to God to make my martyrdom operation a success. I am giving my soul for the sake of God and the homeland."

Abu Naid wrote: "Dad, Mum, forgive me. I am going to carry out a martyrdom operation against a settlement."

Zaqout's mother, asked if she understood his motives, said: "Children are tormented by what they see on television. Israel has left all Palestinians, including children, with no choice but to die."

Another 14-year-old, Haitham Abu Shuqa, was killed last week trying to stage a solo attack on a Jewish settlement with two pipe bombs and a dagger. Pipe bombs are crude devices that use gunpowder from ordinary fireworks.

A 15-year-old girl from Tulkaram on the West Bank was shot dead last month after a stabbing at an Israeli checkpoint and another 15-year-old girl carried out a suicide attack in Jerusalem, also last month.

In a statement that blamed "Israeli massacres" for driving the boys to their deaths, Hamas told teenagers to refrain from acts that might "leave many of them dead by settlement fences".

A Palestinian security source said that police had intercepted several youngsters en route to Jewish settlements in the Gaza Strip with violence in mind in the past few days.

Ibrahim Jaroush, among dozens of children waiting at a Gaza hospital for the arrival of the three boys' bodies, said he wanted to emulate their deed.

"I want to get revenge for the boys killed by Sharon," the 11-year-old said.